1. Field of the Invention
The present invention relates to a method of measuring blood pressure and an apparatus for carring out the method.
More particularly, the invention relates to a method and an apparatus of measuring blood pressure of a subject changing from a squatting state to a standing state.
2. Description of the Related Art
Generally, blood pressure is pressure which blood applies to an artery system receiving blood which has been output owing to contraction of the left ventricle of the heart.
In the other words, blood pressure is pressure within a blood vessel, that is to say, internal pressure.
In detail, blood pressure includes three internal pressures artery, vein and capillary.
However, it is usual that blood pressure is the internal pressure of artery, that is to say, arterial pressure.
The above blood pressure is defined by many factors consisting of contraction or blood volume of the heart, extension or inside diameter of the arterial wall, partial structure and adhesion of blood etc.
That is to say, blood pressure changes according to variation of the heart, blood vessel and circulating blood volume etc.
Hence, by measuring blood pressure it is possible to discover a heart disease, determine a procedure to treat the disease, and judge the effect of the procedure.
Methods for measuring the above blood pressure are divided broadly into a direct method and an indirect method.
The direct method is a method in which blood pressure is measured directly with a transducer connected with a catheter inserted into the blood vessel.
On the contrary, the indirect method is a method in which blood pressure is measured indirectly with a cuff wrapped around an arm of a subject.
The indirect method has advantages that blood pressure is capable of being measured easily in a home owing to simple construction of an apparatus, and that it is to be measured repeatedly during a short time without pain.
Recently, in particular, the use of an automatic sphygmomanometer is now widespread among homes, which sphygmomanometer detects a Kolotkoff sound with a microphone incorporated in the cuff wrapped on the arm, and displays in digital form the maximum and minimum valves of the blood pressure measured.
Therefore, even if people have no expert knowledge, they can easily measure blood pressure with the automatic sphygmomanometer, that is to say, with the indirect method.
The prior indirect method is as follows.
That is to say, as above-mentioned, blood pressure always changes, and so it is often influenced by a posture of a subject whose blood pressure is measured.
Accordingly, when blood pressure is measured, it is necessary to keep the subject in a stable environment in both mind and body.
Hence, using the prior art indirect method, first, a subject should lie on the bed or sit down on a chair.
Additionally, the subject should weaken the force in the front portion from his elbow, and stretch his arm while opening fingers of his hand, assuming a comfortable posture.
In the above-mentioned state, after a cuff is wrapped around his arm, the artery of his arm is pressed by inputting air into the cuff, thereby blood pressure is measured based on the above indirect method.
However, the conventional indirect method has the problem that it is impossible to discover high or low blood pressure which a subject has in case of standing up, that is to say, standing high blood pressure or standing low blood pressure.
The standing high or low blood pressure has been noticed recently.
For example, a splitting headache occuring the moment that a subject stands up is caused by the standing high blood pressure, thereby blood pressure rises up to 160 or more, and also the heart beat increases.
Moreover, orthostatic syncope is caused by the standing low blood pressure.
As above-mentioned, with the conventional indirect method, since blood pressure is measured by means that a subject lies on the bed or sits down on the chair, the standing high or low blood pressure cannot be determined easily.
Accordingly, a subject who has abnormality in his body as he has originally the standing high or low blood pressure, which pressure cannot be determined with the conventional indirect method, will not receive exact diagnosis and treatment.